Protective liquid composition for writing paper



Patented Mar. 13, 1934 PATENT OFFICE PROTECTIVE LIQUID COMPOSITION FOR WRITING PAPER Frank S. Wood, Quincy,

Mass, assignor to Inkset Safety Paper Company, Boston, Mass. a cor-- poration of Massachusetts No Drawing. Application October 13, 1930,

Serial No. 488,545

2 Claims.

This invention relates to a composition to make a safety paper which will show a stain on sulphite paper as well as on higher priced paper-s. By the term safety paper I mean a paper which, after being written upon, will leave tell tale evidence, such as a stain, of any attempts to remove the writing by chemicals.

I am aware that numerous attempts have been madeto produce a chemically treated paper in live colors and white by the use of iodine, potassium and other compositions, both as a separate and as a continuous precess. As a separate operation it has previously been found impossible a to treat anything but a high grade rag paper with an iodine composition, as sulphite paper could not be made a safety paper in a separate operation because it would not take the treatment. The cost of chemically treating a rag paper as well as the high cost of said paper, has made the cost of the finished article prohibitive. Attempts to make safety paper by a continuous operation were unsuccessful because of the cost of the relatively large quantity of chemical solution put in the beaters, much of which was washed out with the water stream necessary to the making of paper. Also the strength of the chemicals injured the brass rolls on the paper machine and caused the paper to discolor.

The novelty of my invention consists primarily in a composition using iodine that will treat low-grade sulphite papers and transmute them, into safety paper that will give a surface stain upon ink eradication; secondarily, using such inare adaptable to papers of difierent colors and finish and cause a penetrating stain to go through the paper and show on the reverse side.

My new composition consists of water as a base, decolorized alkaline tincture of iodine of next smaller volume, glacial acetic acid of next smaller volume, and tannic acid of least volume,

both acids being alkali neutralizing agents.

Decolorized tincture of iodine and tannic acid in the right proportions, with water as a base,

7 in a paper cause a dark stain to appear when ink eradicator is applied, the iodine leaving a stain on the surface of the paper and the tannic acid causing the stain to show through or penetrate to the reverse side. The compounding of the tincture of iodine, which is an alkali, and

the tannic acid, which is an alkali neutralizing agent, produces a result approaching a neutral blend which causes it to stick to the paper, and its action upon the paper making machine or device used in its application is not the least bit injurious. Glacial acetic acid serves to coniplete the neutralization of the composition and prevents the subsequent discoloration of the paper after being treated.

The proportions of the ingredients in my new composition may be greatly varied and yet result in a good safety paper, in fact they must necessarily be varied for different colors, qualities and thicknesses, et? cetera, of paper. The heavier the paper the stronger the solution desired. Also the degree of surface and penetrating stain desired will make a difference in the proportions. I have found, however, that a very satisfactory safety paper results on which a strong, visible stain is left when a chemical is used to eradicate any figures or marks in ink, from the following formula:

I make the right tannic acid solution by dissolving one grain of tannic acid in each gallon of water used.

To fifty gallons of water add fifty grains of tannic acid, in which water the acid quickly dissolves. To this add 640 fluid ounces of decolorized tincture of iodine and 2,637 grains of glacial acetic acid. The result is a clear, slightly opalescent, liquid. The stains may be made lighter by increasing the proportion of water and they may be intensified by decreasing the water proportion. Conversely the stain or discoloration may be darkened by increasing the proportion of tincture of iodine used. The shade of the penetrating stain may be darkened and the sensitivity of the paper to chemicals increased by increasing the proportion of tannic acid. The exact proportions of water, tannic acid, iodine and glacial acetic acid to be used are governed by the paper to be treated, the kind of safety paper desired, the degree of stain desired, et cetera, and one skilled in the art can readily make up a composition to serve the purpose.

Inasmuch as it is often desirable not only to have attempts to eradicate writing show, as by discoloration of the paper, but also to know what letter or figure it was attempted to eradicate, consequently I have had the object in mind of producing a paper having an ink set feature. By ink set I mean that any attempts to eradicate writing on a paper having this ink set feature results in the writing becoming set in the paper and clearly visible. This ink set feature in safety paper is produced with the same ingredients heretofore described in producing a safety paper, and is determined by the proportion of tannic acid to glacial acetic acid. I have discovered that in a gallon of water, for each grain of tannic acid used there should be not less than 40 grains or more than 90 grains of glacial acetic acid, in order to endow the paper with this ink set feature.

I have found that in a 24-lb. buif colored paper that in each gallon of water and grain of tannic acid 57 grains of glacial acetic acid should be used to produce the ink set feature,

and that for canary, pink, gray and goldenrod colored papers the proportion of glacial acetic acid should be from 48 to 57 grains. A solution for blue paper may contain as much as 90 grains of glacial acetic acid, while for a green paper not more than 48 grains should be used. For a 28-lb. paper an extra 8 grains of glacial acetic acid should be used-to provide the paper with the ink set feature. These results areobtained when the proportion of decolorized tincture of. iodine to water is one to ten, although the proportion of said iodine to. water may be varied as stated above, as the ink set feature depends more particularly on the ratio of tannic, acid to glacial acetic acid.

Inasmuch as the cost of decolorized tincture of iodine is relatively high and makes my composition more expensive than is necessary I have found that the proportion of iodine may be materially .reduced by using a cheap alkali such as borax and doubling the quantity of tannic acid and glacial acetic acid used. In

other words the borax provides suflicient alkali to overcome the acid effect resulting from doubling the quantities of tannic acid and glacial acetic acid. Such a mixture to obtain thestain effect in the paper would consist of fifty gallons of water, one hundred grains of tannic acid, 128 fluid ounces of decolorized tincture of iodine, 5,275 grains of glacial acetic acid and 4,070 grains of borax. To obtain the ink set feature it is merely necessary to use tannic acid and glacial acetic acid in the same proportions previously outlined.

In conclusion, it will be understood that various changes may be made in the ingredients and proportions specified without departing from the spirit and scope of my invention; hence I do not intend to be limited to details hereinbefore described except as they may be specifically included in the claims.

What I claim is:

1. A protective liquid composition for writing paper adapted to produce a stain and to set ink thereon upon ink eradication, which consists of one grain of tannic acid per gallon of water, twelve and a half fluid ounces of decolorized iodine tincture, and from 40 to 90 grains of glacial acetic acid. a 2. A protective liquid composition for writing paper adapted to produce a stain on both sides thereon upon ink eradication, which consists of 2 grains of tannic acid per gallon of water, 81 grains of borax, 2 fiuid ouncesof iodinetincture, and from to 180 grains of glacial acetic acid according to thecolor of the paper to be transmuted.

" FRANK S. WOOD. 

